National Marine Week: the journeys through Cornwall’s seas

The water off Cornwall looks still from the cliff path. Underneath it is one long series of departures and arrivals, and that movement is exactly what this year’s National Marine Week is asking people to notice.

National Marine Week is the annual celebration of British seas run by The Wildlife Trusts, and Cornwall Wildlife Trust is marking it along the county’s coast. Despite the name it runs for more than a fortnight, from 25 July to 9 August, a stretch long enough to catch the right tides everywhere from the Tamar to Land’s End. The 2026 theme is “Incredible Journeys”, a focus on the migrations and travels that happen across the seas, rivers and ocean every single day.

Cornish waters are a good place to think about that. They are home to some remarkable marine wildlife, and the trust says the journeys those animals make are a reminder of why better protection across the seas matters. Five of them show what the theme is really about.

Basking sharks, the gentle giants we still can’t fully explain

Basking sharks are among the largest fish in the ocean and among the least understood. We still don’t know exactly where they travel or where they give birth. They were once a common sight off Cornwall. Sightings have become more sporadic as warming seas shift where the sharks choose to go.

Bluefin tuna, back after 60 years

Bluefin tuna have returned to Cornish waters after being absent for more than 60 years. They are among the fastest fish in the ocean and sit near the top of the food chain, powerful apex predators that spend time in the English Channel before moving on to the Bay of Biscay. Some travel as far as the Azores. Their return is one of the more encouraging marine stories in recent years, though the trust warns that strong fisheries management is what will decide whether the comeback holds.

Bottlenose dolphins that keep coming back

Bottlenose dolphins are one of the best-loved animals in British waters. They live in social groups called pods, and the UK supports two kinds of community. Some roam widely offshore. Others are smaller coastal groups that return again and again to the same favourite places.

Grey seals and the space they need

Britain is home to around 95 per cent of Europe’s grey seal population. They spend much of their lives at sea, coming ashore to rest, moult, digest their food and breed. Nobody knows everywhere they go, but monitoring projects have tracked them covering remarkable distances.

If you are lucky enough to spot one along the Cornish coast, keep your distance and keep dogs well away. Disturbance can cause seals significant stress.

Humpback whales, from near extinction to a familiar sight

Humpback whales were pushed to the brink by commercial whaling. Now they are turning up in Cornish waters more and more often, seen on the move between Arctic feeding grounds and the warmer breeding waters around Cape Verde. Their recovery is a picture of what protection can achieve, though Cornwall Wildlife Trust says continued action to safeguard the seas is vital if that recovery is to continue.

Every one of these species is a reminder of how connected the oceans are, and how much depends on protecting the habitats they rely on.

Getting involved this National Marine Week

Cornwall Wildlife Trust is pointing people towards its National Marine Week events page and its Ocean Emergency Fund for anyone who wants to support marine conservation work in the county. The wider week, run by The Wildlife Trusts, asks people to make a simple pledge too, whether that is keeping pollutants out of waterways, choosing sustainable seafood or cutting single-use plastic. For animals that think nothing of crossing an ocean, it is not much to ask.